Air-handling unit is an integrated, box-type equipment operated to carry out one or more of the following operations: circulation, cooling, heating, humidifying, cleaning, dehumidifying, and mixing of air. This is done while controlling the parameters such as temperature, flow rate, humidity, and density. The basic function of an air-handling unit is to take air from outside and condition it by controlling the above-mentioned parameters and supply it to the user. The user may be a house, an office, a building, or any other workplace. A typical air-handling unit has a housing, which is made of metal, where all components of the unit fit into. A cooling coil or heating coil used for cooling or heating dehumidifies or humidifies the air depending on the requirement. A fan, which controls the pressure and flow rate required by the system, is typically a centrifuge with blades of any one of the following types: backward inclined, forward curved, backward curved, and airfoil. Based on placement of the fan, there exist two varieties of air-handling units: blow-through units where the fan is placed before the coil and draw-through units where the fan is placed after the coil. Filters function to remove contaminants and particles of various sizes present in the air. Based on application, filters are classified into panel filters (applied where the use of filtration is less), HEPA filters (applied where high filtration is required), and electrostatic filters (applied where the efficiency of filtration is high). Humidifiers control the humidity in the air. Commonly used humidifiers are of spray type, stream pan type, and stream grid type.